Photogrammetric Measurement System QFoto In-line Quality Control for Support Frames of Collector Modules

QFoto is a 3D measurement system for automatic surveying of concentrating solar collector or other series produced metal structures. It is based on the well-established method of close-range digital photogrammetry and it is typically integrated in parabolic trough and heliostat assembly lines. The system inspects the position and orientation of the mirror support elements, the position of the receiver supports and of other relevant reference points. The software for automatic measurement and analysis can be flexibly adapted to the specific requirements of client’s project. Using a single high-definition camera with self-calibration, the system guarantees high measurement precision even under changing a QFoto has demonstrated reliable operation in collector assembly lines in Europe, North and South Africa, Asia and North America.

Until 2013, the concentrator quality of more than twenty CSP plants totaling 1,500 MW of electrical power and more than ten million square meter aperture area has been checked with the QFoto system.

QFoto works with custom-made high-precision measurement targets and adapters with retro-reflective surfaces for any concentrator type. Specific and robust targets and adapters are available for mirror support positions and angles, for receiver support and rotation axis positions and for other relevant module dimensions. After each measurement, an evaluation report summarizes the main results for all coordinates as well as mirror tilt angles, mirror support angles and distances, including measurement accuracy check. The quality assessment according to defined tolerances evaluates the pass/fail rating for the whole module and indicates it to the operators by a signal light. The output includes statistical quality analysis of the production period.

QFoto System Features

Camera installed on rotating arm above measurement object

Application for parabolic trough, heliostat and dish structures

Automatic measurement (after preparation with targets)

Contact-free 3D measurement

In-situ camera calibration for temperatures up to 55°C

Compensation of thermal expansion of measurement object

Correction of cantilever arm and receiver support tilt

Module rotation axis or optical axis as reference

Calculation of mirror panel tilt angles

Calculation of mirror support angles (optional)

Computation of deviations from nominal values

Comparison of deviations to allowed tolerances

Module quality report

Final pass/fail signal via signal light

Statistical output of process stability (optional)

Uncertainty for 3D coordinates: < 0.5 mm (for x, y, z)

Uncertainty of mirror tilt angles: < 0.2 mrad

Uncertainty for mirror support angles: < 2 mrad

Example Pictures

QFoto measurement summary example from data evaluation report

Control cabinet and camera on pan-tilt-roll head, mounted on rotary arm.